Distributor for continuously operating fuel injection systems

ABSTRACT

In a fuel distributor - in which the fuel to be delivered to a cylinder of an internal combustion engine is dosed by a metering valve - in order to maintain at a constant value the difference between the fuel pressure upstream of and downstream of the metering valve, there is provided a plurality of control valves (one for each cylinder) having a flat seat whose flow passage section is directly variable by a movable membrane. One side of said membrane is exposed to the downstream fuel pressure urging said membrane into a control valve opening direction, the other side of said membrane is exposed to the upstream fuel pressure urging said membrane into a control valve closing direction.

C United States Patent ns1 3,659,628 Bosch et al. [451 May 2, 1972 [541DISTRIBUTOR FOR CONTINUOUSLY 3,054,393 9/1962 schmidt 12a/139 OPERATINGFUEL INJECTION 3,357,448 12/ 1967 Martin.... ..137/501 2,659,425 11/1953leld ..137/501 X SYSTEMS 2,909,191 10/1959 Horton,... ..137/501 [72]Inventors: Walter Bosch, Rommelshausen; Reinhard 3,051,195 8/1962Stenberg.l 137/501 Schwartz Stutt art-Sillenbuch; Gerhard Stumpp,Stuttgargt, all of Germany FOREIGN PATENTS OR APPLICATIONS [73]Assignee: Robert Bosch GmbH, Stuttgart, Germany 26,615 5/ 1911 GreatBritain 137/501 [22] Filed: Oct. l, 1969 Primary Examiner-M. Cary NelsonAssistant Examiner-Robert J. Miller [2l] APPL No" 862875 Attorney-EdwinE. Greigg [30] Foreign Application Priority Data [57] ABSTRACT Oct, 15,1968 Germany P 18 03 066,5 In a fuel distributor in which the fuel to bedelivered to a v cylinder of an internal combustion engine is dosed by ameter- [521 U.s. c1 ..137/so1,123/33 ins valve in Order t0 maintain ai annnsinnt value the dif- [51] Flk 21/00 ference between the fuel pressureupstream of and [ss] Field of Search ..137/501; 12s/32.6, 33 A, 32 1.,dOWnSffeam 0f the metering valve there is Provided a plurali- 123/33 G33 VG ty of control valves (one for each cylinder) having a flat seat'whose flow passage section is directly variable by a movable [56]References Cited membrane. One side of said membrane is exposed to thedownstream fuel pressure urging said membrane into a control UNITEDSTATES PATENTS valve opening direction, the other side of said membraneis exposed to the upstream fuel pressure urging said membrane 2,192,0422/1940 Hoffmann 137/501 imo a control valve closing direction 2,606,0668/1952 Thompson ..137/501 X 2,807,144 9/1957 St. Clair ..137/501 X8Claims,2Drawing Figures DISTREUTOR FOR CONTINUOUSLY OPERATING FUELINJECTION SYSTEMS BACKGROUND OF THE INVENTION This invention relates toa continuously operating fuel injection system for multi-cylinder,externally ignited internal combustion engines. The system is of thetype that includes a distributor having metering valve means which, byvirtue of controlled and simultaneous displacement, regulate the fuelquantities admitted to the fuel injection valves. In order to maintain apossibly constant pressure drop of the fuel across each metering valvein the fuel stream, there is disposed, for each metering valve, acontrol valve, the flow passage section of which is variable by aflexible membrane defining two chambers: in the first of the twochambers the pressure prevailing downstream of the metering valve urgesthe said membrane in an opening direction of the control valve, whilethe pressure prevailing upstream of the metering valve is admitted tothe second of said chambers and urges the said membrane in a controlvalve closing direction.

lt is a desideratum in fuel injection systems ofthe afore-outlined typeto change the flow passage section of the fuel metering valves by meansand as a function of a variable which itself changes in response to theoperational conditions of the internal combustion engine. It is furthersought to obtain, by means of an as constant pressure drop as possiblethrough said flow passage section, a uniform, exact metering of fuel asa function of the magnitude of the flow passage section, whereby suchmetering is independent of the pressures downstream of or upstream ofthe metering valves.

ln a known fuel injection system of the aforenoted type, such asdisclosed in U.S. Pat. No. 2,785,669, the variation of the flow passagesection of the metering valves is performed by axially displacingconical valve needles disposed in corresponding bores. lf the valveneedle is provided with a straight-sided conical head (as is most oftenthe case), the relation between the displacement of the valve needle andthe change in the flow passage section is quadratic. Stated in differentterms, a doubling of the stroke of the valve needle causes a four-foldincrease or a 75 percent decrease of the flow passage section, dependingon which direction the valve needle is moved. lf the side of the cone isarcuate, then the function of the change of the flow passage section isparabolic rather than quadratic. The disadvantage of such ratios residesin the fact that for a linear change of the flow passage section, thevariable affecting the valve needle has to cause a quadratically orparabolically changing displacement thereof which in many cases (forexample, when a space curve is used as the variable) gives rise todifficulties. It is a further disadvantage of all needle valves that fordifferent flow passage sections the flow pattern changes verysubstantially at that location which leads to uncontrollable errors.

It is still another disadvantage of the aforenoted known fuel injectionsystems that the control valve, by means of which the pressure drop atthe metering valve is to be maintained at an as constant value aspossible, comprises a conical valve, the stem-like movable part of whichis controlled by a membrane and is guided in a tube. Since the latter isrelatively narrow, the valve may not operate in a hysteresis-freemanner. Either the valve stem scrapes the wall of the guide tube or thefuel flowing between the tube and the stem affects the setting forcedirected to the valve stem. This hysteresis jeopardizes the effort tomaintain the pressure drop constant at the metering valve. Such aneffort is also disadvantageously affected by the conical seat of thecontrol valve. A valve seat of this type requires a relatively largestroke of the movable valve member in order to fully open the valvewhich is necessary for rapidly obtaining the desired pressuredifference. During this operation the closing spring of said conicalvalve has to be com pressed to a substantial extent which causes achange in the spring force affecting the membrane that regulates theconstant pressure drop. Consequently, it is not feasible to maintain thepressure drop at a constant value.

OBJECT AND SUMMARY OF THE INVENTION lt is a principal object of theinvention to provide an improved fuel injection system in which theaforenoted disadvantages are eliminated.

According to the invention, the flow passage section of the meteringvalves is linearly variable by the axial displacement of a meteringplunger and, further, the control valve is formed by a flat valve seatand a membrane directly controlling the flow passage section of the flatvalve seat under the opposing forces of the fuel pressure upstream ofand downstream of the metering valve.

The invention will be better understood, as well as further objects andadvantages will become more apparent from the ensuing detailedspecication of a preferred, although exemplary, embodiment taken inconjunction with the drawing.

BRIEF DESCRIPTION OF THE DRAWING FIG. l is an axial sectional view ofthe preferred embodiment along line I-I of FIG. 2; and

FlG. 2 is a cross-sectional view along line lI-ll of FIG. l, showing thepreferred embodiment connected to a fuel circuit illustrateddiagrammatically.

DESCRIPTION OF THE PREFERRED EMBODIMENT The distributor according to theinvention comprises a housing l, an intermediate plate 2 and a baseclosure 3, all tightened axially together by means of bolts 4. Theseassembled parts define a plurality of internal cavities generally indicated at la arranged concentrically with respect to the axis ofhousing 1 and spaced equidistantly from one another. Each cavity isfonned of axially aligned bores provided in housing l and base closure3. Between the housing 1 and the intermediate plate 2 there is clamped ametal foil or membrance S which passes radially through each cavity 1adividing each into a chamber 7 and 8.

In each chamber 7, the membrance 5 forms with a stationary valve seat 9,the flat opening of which is disposed coplanar with the clamping planeof membrane 5, a membrane-type pressure drop control valve. Theprovision of a single membrane 5, circular portions of which fonn partof the separate, individual membrane-type control valves, isparticularly advantageous in that the membrance member of each controlvalve has the same thickness and clamped with the same tension. Suchcharacteristics are preconditions for an even operation ofthedistributor device.

Since in the presently described embodiment the distributor has fourcavities la and hence four membrane valves, it is adapted to serve afour-cylinder engine.

The valve seat 9, which is a component machined with precision, is heldin a valve seat holder sleeve l0 which, in turn, is threadedly securedin housing 1. The outer termonus of sleeve 10 serves as a nipple for aconduit 30 which leads to a fuel injection means, such as a fuelinjection nozzle 31 associated with a cylinder of the internalcombustion engine. A radial shoulder 10a of the sleeve l0 is engaged byone end of a coil spring 1l which preferably has a spring characteristicof flat course. The other end of the coil spring 1l engages a springseat disc 12 which, in turn, is in engagement with the membrane 5 andurges the same away from valve seat 9. Thus, the membrane valve is openwhen inoperative. In case the membrane 5, in addition to itsflexibility, has a sufficient resiliency, the coil spring 1 l may beomitted. In such an event, in order to ensure that the valve is openwhen inoperative, the valve seat opening is not coplanar with theclamping plane of the membrane.

Turning now to FIG. 2, base closure 3 is provided with an annularchannel 13 interconnecting four chambers 8 in series in such a mannerthat the first chamber 8 may communicate only indirectly with the fourthchamber in the series through the second and the third chamber. From afuel tank 33 there extends a conduit 34 through a continuouslydelivering fuel pump 35 to an inlet nipple 14 communicating with saidfirst chamber 8. From the fourth or last `chamber 8 of the series, thereextends an outlet nipple 37 to which there is attached a conduit 38Ileading through a pressure maintaining valve 39 back to the fuel tank33.

In an axial bore 16 extending through -the entire distributor there isdisposed a-bearing sleeve 17 surrounded along a part of itsy length byan elastic (e.g. rubber) packing sleeve 18 securing thebearing sleeve 17against axial or angularfdisplacement. The packing sleeve 18 is axiallycompressed by means of a plug 19 urging it against a disc 20 clampedbetween the base closure 3 and the intermediate plate 2. Thus, inaddition to fixedly securing the bearing sleeve 17 in the bore 16,

, the packing sleeve 18 also ensures rthat `no fuel-mayv leak betweenthebearing sleeve 17 on the one hand and the housing 1 and intermediateplate 2 on the other hand.

v ln the axial bore 17a of the bearing sleeve 17 there is disposed ametering plunger 21 which is axially displaceable therein against theforce of a spring and which is provided with a metering or control land21a and a relatively wide, annular, circumferential groove 22adjoiningithe land 21a. The external face of bearing sleeve 17 isprovided with longitudinal grooves 23 which communicate with the axialcylindrical bore 17a of the bearing sleeve 17 through accuratelyidentical, axially parallel, longitudinal metering slots 24. Dependingupon the axial position of the metering plunger 21, the control land 21athereof uncovers a shorter or longer portion of the metering slots 24for communication with the groove 22.

t The bearing sleeve 17 is further provided with radial ports -25 whichestablish a continuous communication between vthe annular groove 22 ofplunger 21 and an annular channel 26. The latter is formed in the baseclosure 3 as the lower terminal portion of axial bore 16 and is definedby portions of the bearing sleeve 17 and the disc 20. From annularchannel 26 there y extend, in a substantially radial direction, channels27 to the The stiness of the membrane 5 and the force of the spring l1are designed in such a manner that in case of a deviation from apredeterminedtpressure drop-betweenthe fuel pressures prevailing inchambers 7 and 8 of a membrane control valve, the'tlow passage sectionbetween themembrane and valve seat 9 continuously changes until saidpredetennined` pressure drop is again obtained.By virtue of a valvestructure described hereinbefore, the duration of such changeoftheannular channel 13 thus establishing communication between annularchannel 26 and chambers 8. The longitudinal grooves 23 of the bearingsleeve 17 communicate with chambers 7 through ports 28. Thus, with eachmembranevalve there is associated a longitudinal groove 23 with itsmetering slots 24. Further, the chambers 7 are separated from oneanother.

OPERATION OF THE PREFERRED EMBODIMENT The continuously operating fuelpump 35 draws the fuel from the fuel tank 33 through the conduit A34 anddelivers it through inlet nipple 14 to the chambers 8 serially connectedby annular channel 13. One part of the fuel returns to the fuel tank 33through outlet nipple 37, conduit 38 and pressure maintaining valve 39.During the course of this circulating fuel flow, the small air bubbleswhich may accumulate under the membrane 5 in each chamber 8 are carriedaway.

The other part of the fuel flows to the annular channel 26 throughchannels 27 which are of sufficient length to have some stabilizingeffect on the fuel stream. Certain pressure losses in annular channel 13may not be avoided during such a fuel flow. lt is a precondition for aneven fuel metering to provide a fuel pressure in the annular channel 26that has a-mean value between the higher inlet pressure at thedownstream end of inlet nipple 14 and the lower outlet pressure at theupstream end of outlet nipple 37. For obtaining such a ,mean pressure,the channels 27 branch o from annular channel 13 at radially opposedlocations thereof whereby the distance between one branch of channel 27and the downstream terminus of inlet nipple 14 is identical to thedistance between the other branch of channel 27 and the upstreamterminus of outlet nipple 37.

From the annular channel 26, `a part of the fuel flows through theradial ports 25 into the annular groove 22 of the metering plunger 21.From the annular groove 22 the fuel, controlled by the metering slots 24(the tlow passage section of which depends upon the axial position ofcontrol plunger 2l) flows into the longitudinal grooves 23 andtherefrom, through ports 28 into each chamber 7 in which a membranevalve is disposed.

flow passage section is extremely short becausek even a smalldisplacement of the membrane changes said flow passage sectionsubstantially. Because of the small displacement ofthe membrane 5, theforce of spring 11 associated with each membrane control valve changesonly slightly. Consequently, the control of the pressure drop proceedsin a very accurate manner or, statedin other terms,the pressure drop issubstantially constant and thus independent of the flow rate of fueldelivered to injection nozzles 3l.

What is claimed is:

1. ln a continuously operating fuel injection system for multi-cylinderinternal combustion engines, yincluding a-dis tributor of known typethat has (A) arbitrarily and simultaneously operable metering valvemeans to determine the fuel quantities to be admitted to fuelinjectionmeans forming -part of said system, (B) at least one first and adjoiningsecond chamber receiving, respectively, fuel under pressure fromupstream of and downstreamof said metering valve means and (C) controlvalve means serving to maintain constant the pressure drop of fuelthrough said metering valve means, the improvement comprising,

A. conduit means associated with each second chamber an connecting thelatter with a fuel injection means,

B. a flat valve seat disposed in the upstream end of said conduit meansand forming the stationary part of said control valve means,

C. a membrane separating each first chamber from an adjoining secondchamber and forming the movable part of said control valve means,l saidmembrane cooperating directly with said flat valve seat, said fuelpressure up'- stream of said metering valve means and prevailing in saidfirst chamber, adapted to urge said membrane towards said flat valveseat to decrease the flow passage section of said conduit means,I saidfuel pressure downstream of said metering valve means and prevailing insaid second chamber, adapted to urge said membrane away from said valveseat to increase the flow passage section of said conduit means,

D. means defining a bore forming part of said metering valve,

E. means for introducing fuel under pressure into said bore,

F. means defining a plurality of axial, parallel metering slots at leastequaling the number of said second chambers, each metering slotcommunicating with said bore and with one of said second chambers and G.a metering plunger forming part of said metering valve and slidablydisposed in said'bore, said metering plunger having a'metering landuncovering to a greater or lesser extent said metering slots dependingupon the axial position of said metering plungerin said bore, the changein the area of the uncovered-portion of each metering slot beinglinearly'proportionate to the axial displacement of saidmeteringplunger.

2. An improvement as'definedin claim 1, wherein said metering valvemeans further includes'a bearing sleeve containying said bore and saidmetering slots; said metering plunger is disposed in each said secondchamber and having a flat spring characteristic, said spring urging saidmembrane away from the opening of said flat valve seat, said opening isdisposed coplanar with the clamping plane of said membrane.

5. An improvement as defined in claim l, wherein said metering valvemeans is disposed centrally and axially of said distributor, saidcontrol valve means comprises a plurality of control valves, onedisposed in each second chamber, said control valves are disposed aboutsaid metering valve means in a circular array, said membranes are partof a single foil member clamped into said distributor and disposednormal to its longitudinal axis.

6. An improvement as defined in claim 2, wherein said rst chambers areinterconnected in series by channel means, said system includes a fueltank and means for introducing fue! under pressure into said channelmeans, one part of the fuel is adapted to be returned to said fuel tankfrom said channel means, the other part of the fuel is adapted to beadmitted to said groove of said metering plunger from said channelmeans.

7. An improvement as defined in claim 6, wherein fuel is admitted fromsaid channel means to said groove of said metering plunger throughradial channels extending from at least the beginning portion and theend portion of said channel means.

8. An improvement as defined in claim 7, wherein said distributorcomprises a housing, an intermediate plate and a base closure heldtogether as a unit, said channel means is provided in said base closurein the fonn of a groove covered by said intermediate plate, said foilmember is clamped between said housing and said intermediate plate; saidhousing, said intermediate plate and said base closure include alignedbores, each last named bore defines a first chamber and an adjoiningsecond chamber.

* t Ik l l

1. In a continuously operating fuel injection system for multicylinderinternal combustion engines, including a distributor of known type thathas (A) arbitrarily and simultaneously operable metering valve means todetermine the fuel quantities to be admitted to fuel injection meansforming part of said system, (B) at least one first and adjoining secondchamber receiving, respectively, fuel under pressure from upstream ofand downstream of said metering valve means and (C) control valve meansserving to maintain constant the pressure drop of fuel through saidmetering valve means, the improvement comprising, A. conduit meansassociated with each second chamber and connecting the latter with afuel injection means, B. a flat valve seat disposed in the upstream endof said conduit means and forming the stationary part of said controlvalve means, C. a membrane separating each first chamber from anadjoining second chamber and forming the movable part of said controlvalve means, said membrane cooperating directly with said flat valveseat, said fuel pressure upstream of saId metering valve means andprevailing in said first chamber, adapted to urge said membrane towardssaid flat valve seat to decrease the flow passage section of saidconduit means, said fuel pressure downstream of said metering valvemeans and prevailing in said second chamber, adapted to urge saidmembrane away from said valve seat to increase the flow passage sectionof said conduit means, D. means defining a bore forming part of saidmetering valve, E. means for introducing fuel under pressure into saidbore, F. means defining a plurality of axial, parallel metering slots atleast equaling the number of said second chambers, each metering slotcommunicating with said bore and with one of said second chambers and G.a metering plunger forming part of said metering valve and slidablydisposed in said bore, said metering plunger having a metering landuncovering to a greater or lesser extent said metering slots dependingupon the axial position of said metering plunger in said bore, thechange in the area of the uncovered portion of each metering slot beinglinearly proportionate to the axial displacement of said meteringplunger.
 2. An improvement as defined in claim 1, wherein said meteringvalve means further includes a bearing sleeve containing said bore andsaid metering slots; said metering plunger is provided with acircumferential groove adjoining said metering land and communicatingwith the uncovered portion of said metering slots.
 3. An improvement asdefined in claim 2, including an elastic packing sleeve disposed betweensaid bearing sleeve and a bore provided in said distributor, meansaxially compressing said packing sleeve to outwardly seal said bearingsleeve and immobilize it in said last-named bore.
 4. An improvement asdefined in claim 1, including clamping means securely positioning saidmembrane, a spring disposed in each said second chamber and having aflat spring characteristic, said spring urging said membrane away fromthe opening of said flat valve seat, said opening is disposed coplanarwith the clamping plane of said membrane.
 5. An improvement as definedin claim 1, wherein said metering valve means is disposed centrally andaxially of said distributor, said control valve means comprises aplurality of control valves, one disposed in each second chamber, saidcontrol valves are disposed about said metering valve means in acircular array, said membranes are part of a single foil member clampedinto said distributor and disposed normal to its longitudinal axis. 6.An improvement as defined in claim 2, wherein said first chambers areinterconnected in series by channel means, said system includes a fueltank and means for introducing fuel under pressure into said channelmeans, one part of the fuel is adapted to be returned to said fuel tankfrom said channel means, the other part of the fuel is adapted to beadmitted to said groove of said metering plunger from said channelmeans.
 7. An improvement as defined in claim 6, wherein fuel is admittedfrom said channel means to said groove of said metering plunger throughradial channels extending from at least the beginning portion and theend portion of said channel means.
 8. An improvement as defined in claim7, wherein said distributor comprises a housing, an intermediate plateand a base closure held together as a unit, said channel means isprovided in said base closure in the form of a groove covered by saidintermediate plate, said foil member is clamped between said housing andsaid intermediate plate; said housing, said intermediate plate and saidbase closure include aligned bores, each last named bore defines a firstchamber and an adjoining second chamber.